1. Field of the Invention
The present invention relates to an electric waste gate actuator for a turbocharger, and more particularly, to an electric waste gate actuator for a turbocharger, in which the inside of a housing is divided into an upper portion and a lower portion to thereby prevent foreign particles generated in a decelerator from being introduced into a driving motor.
2. Description of the Related Art
Generally, power generated by an internal combustion engine is dependent on a mass of air and an amount of fuel that may be supplied to the internal combustion engine. In order to increase the power of the internal combustion engine, it is necessary to supply a larger amount of combustion air and fuel. The increase in the power of the internal combustion engine may be achieved by increasing a cubic capacity or rotational speed of an intake engine. However, the increase in the cubic capacity leads to an expensive internal combustion engine having a relatively heavy weight and a large size. In particular, the increase in the rotational speed accompanies serious problems and disadvantages in a relatively large internal combustion engine.
Supercharging has been often adopted as a technical solution to increasing the power of the internal combustion engine. Supercharging refers to precompressing combustion air using an exhaust gas turbocharger or a compressor mechanically driven by an engine. The exhaust gas turbocharger basically includes a turbine and a compressor connected to a common shaft and rotating at a constant rotational speed. The turbine converts uselessly exhausted energy into rotational energy through exhaust gas. The turbine drives the compressor. The compressor sucks new air and supplies precompressed air to individual cylinders of an engine. An increased amount of fuel is supplied to a relatively large amount of air in the cylinder. As a result, the internal combustion engine outputs higher power. Therefore, a combustion process is additionally influenced preferably, and the internal combustion engine has a higher total efficiency level. In addition, a torque profile of the internal combustion engine, which is supercharged by the turbocharger, may be formed very preferably.
Since a series induction motor from a vehicle manufacturer uses an exhaust gas turbocharger, it may be considerably optimized without a structural interference with an internal combustion engine over a wide range. Generally, the supercharged internal combustion engine has a relatively low specific fuel consumption and a lower pollutant emission rate. Furthermore, since the exhaust gas turbocharger itself acts as an additional silencer, the turbo engine is silent at the same power level as compared to a typical intake engine.
In an internal combustion engine having a wide rotational speed range (for example, an internal combustion engine for a car), a high charging pressure is required at a low rotational speed of an engine. To this end, a charging pressure control valve, called a waste gate valve, has been applied to a turbocharger. By selecting a relevant turbine casing, a high charging pressure is formed at a low rotational speed of an engine. The waste gate valve limits a charging pressure to a predetermined level according to the increase in the rotational speed of an engine.
In the conventional electric waste gate actuator having the above-described functions, gears are disposed on a motor, a sensor, and an electronic control unit (ECU), and therefore, foreign particles generated in grease used in the gears and generated by abrasion of the gears are introduced into a motor terminal, an ECU, and a sensor, causing the degradation of performance. Furthermore, if a sensor directly measuring a rotation of an output shaft is used due to spatial limitation, there is difficulty in a structure for supporting both ends of a gear.